A Randomized, Double‐Blind, Placebo‐Controlled Multicenter Efficacy and Safety Study of Methotrexate to Increase Response Rates in Patients With Uncontrolled Gout Receiving Pegloticase: 12‐Month Findings

OBJECTIVE: To assess 12‐month safety and efficacy of pegloticase + methotrexate (MTX) versus pegloticase + placebo (PBO) cotherapy in a PBO‐controlled, double‐blind trial (A randomized, double‐blind, placebo‐controlled, multicenter, efficacy and safety study of methotrexate to increase response rates in patients with uncontrolled gout receiving pegloticase [MIRROR RCT]). METHODS: Patients with uncontrolled gout (serum urate level [SU] ≥7 mg/dl, oral urate‐lowering therapy failure or intolerance, and presence of one or more gout symptoms [one or more tophi, two or more flares in 12 months, gouty arthropathy]) were randomized 2:1 to receive pegloticase (8‐mg infusion every 2 weeks) with blinded MTX (oral 15 mg/week) or PBO for 52 weeks. Efficacy end points included proportion of responders (SU level <6 mg/dl for ≥80% of examined month) in the intent‐to‐treat population (ITT) (all randomized patients) during month 6 (primary end point), month 9, and month 12; proportion with resolution of one or more tophi (ITT); mean SU reduction (ITT); and time to SU‐monitoring pegloticase discontinuation. Safety was evaluated via adverse event reporting and laboratory values. RESULTS: Month 12 response rate was significantly higher in patients cotreated with MTX (60.0% [60 of 100] vs. 30.8% [16 of 52]; difference: 29.1% [95% confidence interval (CI): 13.2%‐44.9%], P = 0.0003), with fewer SU discontinuations (22.9% [22 of 96] vs. 63.3% [31 of 49]). Complete resolution of one or more tophi occurred in 53.8% (28 of 52) versus 31.0% (9 of 29) of MTX versus PBO patients at week 52 (difference: 22.8% [95% CI: 1.2%‐44.4%], P = 0.048), more than at week 24 (34.6% [18 of 52] vs. 13.8% [4 of 29]). Consistent with observations through month 6, pharmacokinetic and immunogenicity findings showed increased exposure and lower immunogenicity of pegloticase when administered with MTX, with an otherwise similar safety profile. No infusion reactions occurred after 24 weeks. CONCLUSION: Twelve‐month MIRROR RCT data further support MTX cotherapy with pegloticase. Tophi resolution continued to increase through week 52, suggesting continued therapeutic benefit beyond month 6 for a favorable treatment effect.